Catalytic conversion process



Nov. 7, 1944. M. T. CARPENTER CATALYTIC CONVERSION PROCESS Original Filed Jan. 12, 1938 R Y mm m ma m m n l m A QEQQQ QVQR have heretofore been deemed essential.

Patented Nov. 7, 1944 CATALYTIC CONVERSION PROCESS Morris T.,-Carpenter, Chicago, 111., astlgnorto Standard Oil Company,

ration of Indiana Chicago, Ill., a corpo- Original application January 12, 1938, Serial No. 184,669. Divided and this application June 14, 1941, Serial No. 398,047

16 Claims.

. This invention relates to a catalytic conversion process and it pertains more particularly to the catalytic conversion of hydrocarbons of various kinds and boiling ranges into high quality motor fuel. This is a division of my co-pending application Serial 184,669, filed January 12, 1938, now

U. S. Patent 2,273,089.

. Anobject of my invention is to provide an 'im- 4 proved method for supplying the heat required for catalytic cracking. A further object is to provide a method for using simple catalyst chambers for catalyticcracking, thereby avoiding the expensive, complex, cumbersome chambers that A further object is to utilize more effectively the normally liquid and normally gaseous portions of feed stock to obtain maximum yieldsof highest quality motor fuel therefrom. A further object is toyimprove the thermal efficiency of a catalytic cracking system to utilize available heat in all parts of the system to the fullest extent, and at the same time to avoid the necessity of using an extraneous heat transfer fluid system.

It haslong been known that catalyticcracking will yield high quality motor fuels. Economically,

however, such processes have not been able to compete successfully with thermal processes because of (1) the expensive construction, repair and operat ng costs of complicated catalytic chambers, (2) the expense and difficulty of catalyst regeneration, and (3) the poor heat economy of prior catalytic systems. An object of my invention is to overcome these difficulties and ,To supply the heat for the cracking reaction I superheat the incoming stock to a certain extent and supply therest of the necessary heat by the introduction of .superheated gases at that point of the system at which the cracking is occurring. As the catalyst in the top of the chamber becomes spent (due to carbon deposition or to other causes), the reaction at that point practically ceases, and the reaction zone moves along the chamber to the next adjacent portion of the catalyst. To avoid too long a time of contact with the hot catalyst, and to avoid excess coke deposits,- both the feed and the hot gases may be by-passed around the spent catalyst and introduced directly into the'current reaction zone. The hot cracked products do preheat the cata- :lyst beyond the reaction zone, but the necessary heat to effect substantial cracking is supplied only to the zone where it is desired for cracking to take place. Thus there is no danger of overcracking due to too long time of contact.

Revivification is also effected in a gradually moving zone or wave front, the temperature and oxygen content of regeneration gases being regulated to-prevent over-heating. In regeneration cool gases may be used to remove the exothermic heat of combustion, just as in the case of catalytic cracking hot gases areusedto supply the necessary endothermic heat. The hot spent regeneration gases. give up their heat to gases entering the catalytic cracking system.

A feature of the invention is the utilization oi hot gases rich in hydrogen, both for maintaining the desired temperature at any given reaction zone and to prolong the life of. the catalyst. The

' hydrogen tends to keep the cat'alyst clean and 'to improve the quality and yield of the finished products:

Another feature is the saving in compressor costs and the increase in gasoline yields effected coming stock, condensable hydrocarbons sepashows simply a flow diagram with the furnaces,

from other sources.

rated from the reaction products or obtained Gases from a. high pressure stabilizer may be either returned to this absorber at relatively high pressure or introduced with the feed stock to effect what is commonly termed gas reversion, i. e., a chemical combina tion of gases -with liquids to form high quality motor fuels of intermediate boiling range. n

The invention will be more clearly understood from the following detailed description read in connectionwith the accompanying drawing which forms a part of this specification and which catalystchambers, towers, etc. diagrammatically represented in vertical section.

The invention will be described as applied to the conversion of Mid-Continent gas oil into high quality, high octane number gasoline. It should be understood; however, that the invention is equally applicable to all cracking stocks, particularly stocks of the naphtha thru gas oil boil-' ing range. Heavier stocks, including residual gaseous hydrocarbons may be caused to react in the cracking process to-effect what is called gas reversion.

The gas oil feed stock is introduced through line l and branched line H to the top of absorber tower l2 which is provided with suitable baflle or bubble plates 83, and into which hydrocarbon gases are introduced at the base through line It. If desired, some or all of the feed stock may be by-passed through line 15 to line 13 through which the enriched feed stock is withdrawn from the absorber.v The charging stock is then pumped by pump H or passed through line l3, to line l9, heat exchanger 20 andv pipe still or equivalent heater 2|. This still is preferably operated at approximately atmospheric pressure 28a at points above the various catalyst beds 29 and 231:, which are supported on conventional screen supports 30 and 3011. These reaction chambers may be from about 20 to 50 feet high and about to teeth diameter. The trays may be spaced at intervals ranging from about 1 to 2 feet and the catalyst on each tray may vary in thickness from 4 or 5 inches to about a foot or more. It will thus be seen that I have provided a series of contiguous catalyst beds, each separated from adjacent beds by an open space, and I have provided means for introducing hot feed gases above the catalyst on each tray.

As a catalyst I prefer to employ small cyiin drical pellets about V8 to? to an inch in height and diameter, which pellets are made by admixing acid treated Death Valley clay with about 25% of water to form a slurry, forcing this slurry through an orifice under about 1000 pounds pres; sure to give a "spaghett and baking this spaghetti for several hours at about 1050 F. It

' should be understood, however, that I may use any activated hydrosiiicate of alumina catalyst;

other natural clays or acid-treated natural clays may be substituted for Death Valley clay, and synthetic clays may be prepared by precipitating alumina on silica gel. I prefer to employ about to 40 moi. percent of alumina in the composition, about to usually being the optimum. This optimum percentage of alumina may be obtained in natural clays such as Olmstead, Attapulgus, Floridin earth, montmorillonite, Filtrol, diatomaceous earth, fullers earth, etc. by acid or other chemical treatment. Activated clays may be "used as such or they maybe impregnated with from about '1 to 10% of oxides of nickel, copper, manganese or other catalytic materials which have the known properties of promoting hydrogenation and desuliurization and/or which may promote catalyst regeneration. It should also be understood that instead of the clay type catalysts I may employ magnesium chromite, boron silicate or any other known catalytic cracking catalyst of proven effectiveness. The particular catalyst per se forms no part of my'present invention. g G ases rich in hydrogcn and containing s bstocks, may be catalytically cracked and normally stantial' quantities of methane, ethane, ethylene, etc. are withdrawn from thetop of absorber l2 through line 3| and passed through heat exchanger 32, pipe still or equivalent heater 33,

and thence through line 34 to manifolds 35 and- 35a. These manifolds are provided with valved side lines 36, 31, 38 and 33, 33a, 31a, 38a and 39a,

respectively, which communicate with the open spaces above each catalyst bed in the same way that valved branch lines 24 to 21 and 24a to 21a,

' respectively, communicate therewith.

Fluids from the reaction chambers may be selectively withdrawn through lines 40 and Mia through line II which leads through exchanger 20 to fractionator 41. They may likewise be selectively withdrawn through line 32 which leads through heat exchanger 32 to vent line 03.

They may also be selectively withdrawn through.

line H.

Hot gases, preferably flue gas containing the desired amounts of oxygen, may be introduced through line selectively into manifold 35 or manifold 35a. A.purging fiuid such as steammay be introduced through the same lines. Cold rebe understood, of course, that gases of any composition and at any desired temperatures may be introduced at desired pointsinthe reaction cham- {i0 bers, either through line 45 or line 46.

It should be understood that while I have disclosed only two reaction chambers, I contemplate the use of any number of such chambers as may be required for a given installation, due consideration being given to the time necessary for catalyst regeneration. While one chamber is "on stream, one or more of the chambers are being revivified. This is familiar practice and needs,

no further detailed description.-

As hereinabove stated, I introduce the hot charging stock gases or vapors at about 850 F. through branch line 24 into the top of reaction chamber 28, the valves in lines 25, 26 and 21 being closed and catalyst chamber 23a being cut off for revivification. Since the contained heat of the charging stock may not be sufficient to supply the endothermic heat of cracking, I introduce through branch line 36 superheated gases from pipe still 33, these gases being of a temperature of about 1000 to 1500" F. With the heat thus imparted in the top catalyst bed, the gas oil will crack to form the desired gasoline compounds, together with certain radicals which may chemically combine with the introduced gases to form additional amounts of high quality gasoline. The

, cracked gasoline and gases from the top catalyst zone passes down through the otherzones of the tower, thus preheating them and bringing them up to reaction temperature. Since the lower catalyst beds are at a lower temperature thanthat required I for cracking, there will be no appreciable decomposition of the reaction products formed in the upper ,bed, and, in fact, there may be a partial hydrogenation of the cracked gasoline as the components move downwardly through the tower.

When the upper catalyst bed becomes substantialiy deactivated, because of coke deposits, etc., I open valve 28 to by-pass part or all of the incoming hot stockaround the spent catalyst zone. I may at the same time open valve 31 to supply superheated fixed gases and unreacted vapors for supplying the endothermic heat of cracking; I prefer, however, to have these gases pass through the top catalyst layer until that through lirie 4 I. to fractionator 41 which may conously throughout the length of the column, but

"this renders temperature controldifllcult to 'obtain, and it also makes it necessary for the crackedproducts from the top of the tower to halye too long a time of contact with the catalyst atreaction temperature. My invention relates primarily to the catalytic conversion of the hydrocarbons in a particular zone which gradually moves from the top ofthe tower to the bottom thereof. By effecting the reaction in this manner the tower can be operated for a long period of time, before regeneration is necessary, and, accurate temperature control can be obtained allalong the line. While reaction chamber. 28 is on stream, chamber 28a is purged, revivified and again purged preparatory to once more going "on stream." The purging'may be effected by steam or by vacuum. Regeneration is efleoted by bum-' ing "the carbon from the catalyst at a temperature of not higherthan about 1000 to 1050" F.

' a This temperature may be accurately controlled by regulating the amount of oxygen in the hot flue gases which are preierably introduced through line 45, header 35a and branch lines 35a, etc. It should be understood,-however, that the exothermic heat of combustion can be dissipated in part by the use of cold gases from line, -header 23a and branch lines 24a, etc. Here again I use the parallel systems for introducing fluids of diiferent temperatures in regulated amounts'to maintain the desired temperatures at each and every point of the catalyst chamber.

'If any catalyst bed tends to, become overheated the hot gases are immediately shut off and cold gases introduced 'at that point. 'The valves in the side lines may beiautomatically operated in accordance with'temperature conditions in the catalyst bed. Such automatically operated valves are well known to those skilled in the art and they ,will therefore not be described in further detail.

The hot gases which leave the reaction chambers at about 1050 F. are passed through line 42 to heat exchanger 32 wherein they give up their .heat to the gases entering the system through line 8|. This efiectively utilizes the heat Of'regeneration for supplying the endothermic heat of cracking. Sometimes, to produce better heat transfer coefficients, it may be desirable to use the hot spent regeneration gases for generating steam. i

After regeneration, the catalyst chamber is purged, the purged gases being removed through vent line. Catalyst. chamber. 28a is then ready togo on stream as soon as all of the catalyst beds in chamber 28 have become spent. Just as exchanger 32 picks up the heat from the spent regeneration gases, so that the heat sist or a column with from 10 to 40 trays or bubble plates. Material above the gasoline boiling range is withdrawn from the base of the frac Y tionator through line 45,; This material, called .cycle stock," may be stored for subsequent catalytic cracking in the same system, it may be passed to another catalytic or thermal cracking unit, or may be recycled with the incoming ifeed l stock.

Gasoline and gases from the top of fractionator l1 are conducted through line 0 to water condenser 50 which liquefles most of the gasoline a large part of the butanes and some propane and lighter hydrocarbons. These liquids are separated in separator a part of them being recycled through line 52, pump 53 and line 54 This tower is preferably operated at about'200 to 400 pounds pressure per square inch and is provided-with a suitable reboiler 59 at its base. Here again we may employ from about to 40 bubble plates 50. Stabilized gasoline is withdrawn from '9 the base of the tower through line 5|, heat exchanger 56, water cooler 52 and line 53 to a suitablestorage tank. This gasoline is characterized against" oxidation and gum formation, and an extraordinarily high octane number which may range from 75 to 95. l Vapors from the top of the stabilizer are with-.

drawn through line 54 to the water condenser 55, wherein they are partially liquefied, "the liquids being. separated from the gases in pressure separator 66. A portion of these-liquids are recycled through line 61, pump '68 and line '39 for reflux in the stabilizer tower. The'remainiug liquids are withdrawn through line 10; these 56 may be recycled through line I! to line I! (since the gases are under suflicient pressure 60 may be'introduced' through line I2 and line 13 through line H in absorber l2. The bulk of the ,gases introduced through line H, however, will usually come from low pressure separator 5|, the gases being withdrawn therefrom through line ll, compressed by compressor and introduced through line 16 to line H at the base of the absorber. These gases may contain upwards of of hydrogen. Bypassing them through the absorber, all of the condensables are removed therefrom before they are heated to the high temperatures which might be destructive of propanes and butanes. If methane or other fixed gases tend to accumulate in the system they top of absorber II. On the other hand, if the nature of the charging stocks makes possible the consumption of more gases than are produced, additional hydrogen or gaseous hydrocarbons line 10.

While I prefer to operate the absorber at a pressure of .about 50 to pounds per square inch, it should be understood that higher pressures may be used, particularlywhen it is deby an extremely low sulfur content, a stability to. avoid the necessity of compression), or they may be vented therefrom through line IT at the may be introduced into the system through 'strued as broadly as the siredto incorporate large amounts of gaseous hydrocarbons into the liquid feed stock to effect what is commonly referred to as gas reversion} The'catalysts and operating conditions for cata-J lytic cracking seem to effect to a considerablei extent the combination of normally gaseous hydrocarbons with normally liquid hydrocarbons to form high quality motor iuels of intermediate boiling range. Likewise, the hydrogen content of the gases introduced through headers 35 and 35a not only has a noticeable effect in keeping the catalyst clean for a relatively long period of time, but it appears to effect a certain degree of hydrogenation of the.re action products.

While I have described in detail a preferred embodiment of my invention, it should be understood that I do not" limit myself to any of the details hereinabove set forth except as defined by the following claims, which should be con prior art will permit.

I claim: A

1. The method of catalytically cracking hydrocarbon charging stocks of the classconsisting of gas oils, heavier stocks and residual stocks which method comprises vaporizing and heating said charging stocks to a temperature of about 8j00 to 1050 F., contacting said heated charging stock vapors in a high temperature part of a conversion zone with a catalyst consisting essentially of silica and alumina wherein silica is the major component and alumina is a minor com ponent, introducing a superheated gas containing at least 20% of hydrogen at a temperature of 1000 to 1500 1?. into the conversion zone in such amounts as to effectively prolong the life of the catalyst, subsequently passing said gas and vapors through a lower temperature part of said conversion zone whereby conversion products are partially hydrogenated, separating a recycle gas containing at least 20% hydrogen from the reaction products, recycling said gas to said conversion zone and fractionating the remaining products to obtain a hydrocarbon fraction of the gasoline boiling range and lighter and heavier hydrocarbon fractions respectively.

2. The method of claim 1 wherein the catalyst contains about to 40 mol per cent of alumina.

3. The method of converting a liquid hydrocarbon chargiii'g stock for producing substantial "yields of high quality high'octane number gasoline which method comprises vaporizing and heatin said charging stock to a temperature of at least about 925 passing said heated vapors through a series of contacting zones of .solid catalyst particles containing at leastabout 15 'mol ercent of alumina in composition, countercurrently contacting a hydrogen-containing gas with an absorber oil for removing condensible normally gaseous hydrocarbons therefrom and to produce a scrubbed gas containing at least of hydrogen, heating said scrubbed gas to a tem-' ,perature substantially higher than the tempera ture to which the charging stock vaporsare heated and to a temperature of at least about 1000" F., introducing at least a part of the superheated hydrogen-containing gas with the charging stock vapors entering at least' one of the contacting zones efieeting high temperature conversion in the first of saids'eries of contacting zones and subsequently utilizing other zones of said series,

in succession, for eflecting conversion at high conversion temperature.

4. The method of claim3 wherein the charging stock consists essentially of gas oil and heavier hydrocarbons, wherein the catalyst consists ier hydrocarbons, wherein the catalyst consists essentially of acid treated montmorillonite clay and wherein the reaction is essentially catalytic cracking, the introduced hydrogen-containing gas tending to keep the catalyst clean and supplying heat for the catalytic cracking reaction.

6. The method of making a high quality gasoline fraction from heavier hydrocarbon charging stock which method comprises vaporizing and heating said charging stock to a cracking ternperature within the approximate range of 800 to 1050 F., passing the heated vapors in series through a plurality of separate contacting zones containing silica-alumina catalyst material, em. ploying a temperature in the first contacting zone sufliciently high to effect substantial catalytic cracking, utilizingother of said separate contacting zones after the first, in succession, for effecting conversion at said cracking temperature, and employing a temperature in a zone subsequent to the cracking zone sufiiciently low to prevent "appreciable decomposition and to effect a partial hydrogenation whereby the quality of the of high quality motor fuel by endothermic reaction, which method comprises vaporizing and heating said charging stock to substantially conversion temperatures, passing said vapors through a seriesof contacting zo'nes containing a solid conversion catalyst, separately heating a gas to a temperature above said conversion temperature, introducing at least a part of said heated gas into at least one of the series of contacting zones, initially maintaining the first zone of the series at said conversion temperature and the subsequent zones at a lower temperature, and subsequently maintaining other ,of said zones after the first, in succession, at said conversion temperature by the introduction of said separate- -ly heated gas.

line fraction from heavier hydrocarbon charging stock, which method comprises vaporizing and heating said charging stock toateinperature within the approximate range of 800 to 1050 F.,

- passing the heated vapors in series through a plurality of separate catalyst beds containing silica-alumina catalyst material whereby endothermic conversion of the charging stock is effected with the deposition of coke deposits on said catalyst material causing deactivation thereof, regenerating deactivated catalyst material by passing hot oxygen-containing gases through said separate catalyst beds in series whereby the coke deposits are burned with the liberation of heat, introducing cool gases between said separate beds in amounts suflicient to control the temperature of the catalyst in said beds and utilizing heat dethe charg veloped by the combustion of said coke deposits to supply heat in said conversionstep.

The method of-ciaim. 9 wherein the amount of cool gas introduced between said catalyst beds in the regeneration step is suflicient to prevent catalyst temperatures from substantially exceeding about 1050 F.

11. The method of eirecting hydrocarbon conversion in a system employing a plurality of reaction zones of which at least one is on-stream while at least one other is undergoing regeneration, which method comprises arranging a silicaalumina catalyst in a series of separate beds in each zone, passing heated hydrocarbon vapors through the catalyst beds in a zone which is onstream while maintaining said zone at a temperature within the approximate range of 800 to 1050 F. whereby endothermic conversion is eiiected and the catalyst becomes deactivated because of coke deposits, simultaneously passing an oxygen-containing gas in series through the catalyst beds in the zone which is undergoing regeneration whereby coke deposits are burned from the catalyst with liberation of heat, introducing relatively cold gases into said second zone between the catalyst beds and in amounts suflicient to control the temperature thereof and to keep said temperature within-desired limits, utiiizing at least a portion of the heat 01' combustion of said coke deposits for supplying endothermic heat of conversion in said system and periodically eflecting endothermic conversion in zones which have undergone regeneration and eflfecting regeneration in zones which have undergone endothermic conversion.

12. The method, of claim 11 wherein the amount of cooled gases introduced between catalyst beds in the zone undergoing regeneration is suilicient to prevent temperatures in said beds from substantially exceeding 1050 F.

13. The method of claim 11, wherein the heat oi combustion is utilized by the steps of heating a gas by heat exchange with combustion products from the zone which is undergoing regeneration ,and introducing said heated gas into the zone cracking catalyst under conditions for eflecting cracking and the deposition oi coke on the catalyst, discontinuing the passage of said stock through said first series of separate catalyst beds when the catalyst becomes substantially deactivated because of coke deposits and transferring the passage of said vaporized stock through a second series of separate beds of solid cracking catalyst, purging hydrocarbons from the series oicatalyst beds from which the passage oi vaporized charging stock has been discontinued, passing an oxygen-containing regeneration gas in series through said purged catalyst beds under conditions for burning said coke deposits from said catalyst and generating heat of combustion, introducing relatively cold gases between said separate beds while regeneration gases are being passed therethrough for keeping temperatures within'desired limits throughout said series of catalyst beds, absorbing a part of the generated heat of combustion in a heat transfer medium and liberating heat from said heat transfer medium in catalyst beds simultaneously with the passingvof vaporized charging stock thereto.

15. The process of claim 14 in which the cracking catalyst consists essentially of a silica-aluoline fraction from a heavier hydrocarbon charging stock which method comprises contacting vapots of said charging stock at an endothermic conversion temperatureby passing said vapors through a plurality of beds of a catalyst material for producing endothermic conversion with the deposition of carbonaceous deposits on the catalyst material, regenerating said catalyst material by passing hot oxygen containing gases through said catalyst beds in series whereby the carbonaceous deposits are burned with the liberation of heat, introducing cool gases between said beds in amounts suflicient to control the temperature of the catalyst therein, and utilizing heat developed by the combustion of said carbonaceous deposits for supplying heat in said en-' dothermic conversion step.

' MORRIS T. CARPENTER. 

